Direct Formation of 2-Substituted 2<i>H</i>-Indazoles by a Pd-Catalyzed Reaction between 2-Halobenzyl Halides and Arylhydrazines
Nayyef Aljaar, Mousa Al‐Noaimi, Jürgen Conrad, Uwe Beifuß
Abstract
A direct and operationally simple method for the regioselective synthesis of 2-aryl-substituted 2H-indazoles is reported. The Pd-catalyzed reaction between easily available 2-bromobenzyl bromides and arylhydrazines employing Cs2CO3 as the base and t-Bu3PHBF4 as the ligand in DMSO at 120 °C in a sealed tube delivers the 2-substituted-2H-indazoles in a single synthetic step with yields up to 79%. The new method is based on a regioselective intermolecular N-benzylation followed by intramolecular N-arylation and oxidation.
Topics & Concepts
RegioselectivityChemistryHalideCatalysisIntramolecular forceArylIntermolecular forceCombinatorial chemistryLigand (biochemistry)Medicinal chemistryBase (topology)Reaction conditionsOrganic chemistryMoleculeAlkylReceptorBiochemistryMathematicsMathematical analysisCatalytic C–H Functionalization MethodsCatalytic Cross-Coupling ReactionsCyclopropane Reaction Mechanisms